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Why do schizophrenics hallucinate, hear voices? Mapping uncovers brain shrinkage
Schizophrenia Update, December 2002
By: Veronique Mandal, Star Health-Science Reporter
Cutting-edge brain mapping techniques have allowed scientists here to link schizophrenia to a shrinkage of grey matter, proving definitively that the disease is no less physical than cancer or diabetes.
The deterioration can begin at childhood and amplifies with each psychotic episode, researchers at the Montreal Neurological Institute of McGill University have found.
"There is such a terrible stigma about this disease but it is actually no different than any other physical brain disease," said researcher Dr. Tomas Paus.
In one of the most advanced labs in North America, worth $35 million, Paus and his team used advanced MRI equipment and Positron Emission Tomography (PET) scanners to track what schizophrenia does to grey matter. The effects on children were espcially profound. Patients with early-onset schizophrenia had a much greater loss of grey matter, especially in the frontal and temporal lobes, as those who contracted it later in childhood, according to the Paus research, published in the Archives of General Psychiatry.
"This is consistent with evidence suggesting that abnormalities in frontal and temporal lobe connections underlie the symptoms of schizophrenia," said Paus. "Thus a specific pattern with schizophrenia develops across the adolescent years."
Deterioration in the prefrontal cortex of the brain affects verbal memory, attention, reasoning, aggression and meaningful speech, helping explain why schizophrenics sometimes babble incoherently.
Overactivity in the frontal and right temporal lobes was associated with auditory hallucinations, a common and debilitating symptom of schizophrenics who claim they hear voices.
Loss of volume in the temporal lobe also affects the limbic system, located deep in the brain and containing the hypothalmus, amygdala and hippocampus. Those are responsible for emotions and memory and abnormalities are associated with the delusions, hallucinations and disordered thinking common among schizophrenics.
Research labs around the world have added to the bank of physical evidence that explains schizophrenic behaviour.
Studies at the University of Toronto and other centres show an overproduction of the chemical dopamine, which is closely linked to psychotic symptoms in schizophrenia. Research at Johns Hopkins University, using a newly developed 3-D diffusion tensor MRI, points to evidence that schizophrenia involves decreased communication between the right and left sides of the brain and that miswiring between nerve cells impairs information processing and co-ordination of mental functions.
Evidence that parts of the brain are not communicating is also found in the corpus callosum, which connects the two halves of the brain and is responsible for relaying information back and forth. It is thicker and longer in the schizophrenic brain. The ventricles, hollowed out cavities containing cerebrospinal fluid, are also enlarged, causing emotional flatness, lack of expression and a lack of pleasure or interest in life.
Children whose mothers were underweight at the end of pregnancy had a three- to four-times greater chance of developing schizophrenia, according to research in Finland. Low birth weight and thinness during childhood also increased risk of the disease.
Researchers from the New York State Institute of Psychiatry, writing in the Archives of General Psychiatry, found in one study that children whose fathers were age 50 and over at the time of their birth were also likely to have a psychotic episode.
At the University of Florida's Brain Institute, researchers have discovered subtle differences in 10 brain structures which could indicate schizophrenia.
The influenza virus is also under scrutiny. A study by researchers at King's College Hospital in London, England, found the virus present in 13.2 per cent of mothers who had children with schizophrenia. All but two occurred during the fourth, fifth and sixth months of pregnancy.
The area affected is responsible for language, processing information, reasoning, planning and abstract thought.
A study published in 2001 in Proceedings of the National Academy of Sciences, reported that retroviruses, which contain RNA instead of DNA, may play a role in the development of schizophrenia in some individuals.
Adding to the suspicion that viruses or infection affect fetal brain development, scientists have observed that more schizophrenics are born in winter and early spring and in cities with very cold winters.
GRAPHIC: AFFECTED AREAS OF THE BRAIN: Source: www.diseases-explained.com. Star graphic: Susan Thomson-Stamcoff; CEREBRAL SLEUTH: At his lab in Montreal, neuroscientist Tomas Paus scans the brain. Photo special to The Star: Marcos Townsend